Constans, AE4, Lyons, 346-348 AD.

CONSTANS-PF AVG, laurel and rosette-diademed, draped, 
cuirassed bust right.
GLORI-A EXER-CITVS, two soldiers holding spears and shields 
with one standard between them. Y on banner.

Mintmark: SLG.

RIC VIII Lyons 24.

From Dane's collection, August 2010.

Known mintmarks for this RIC number:
PLG
SLG

Note: Although the mintmark is mostly off the flan,
using a magnifying glass, the top parts of the letters SL 
are visible. Apart from that, the Y on the banner plus this 
obverse legend, its unusual legend break position and the 
bust type makes the identification certain.